It depends...
While most jurisdictions do not hold one guilty for intentionally firing at some one out of reasonable fear of imminent death or grievous bodily harm, the defender must be always mindful of civil liability.
The practice of modifying or removing safety devices is inherently risky. Any competent plaintiff's attorney will file suit alleging that you shot the intrudent acidentally. Said opportunistic bottom feeder will claim that deviation from the factory specifications constitutes a per se negligent action on your part.
Unfortunately, there are gullible judges and juries who have bought this rationale and have bankrupted good and law-abiding people. Go figure, O.J. is free.
At any rate, the unquestionable and best practice is to refrain from any modification of any of the safety devices on guns, aircraft, powerboats and cars. On a M1911, these parts would be, fundamentally, the firing pin safety, the grip safety and the safety levers. Now, before everyone gasps and tells me I must be wrong about springs and grip safeties, please allow me to explain. It depends.:barf: As long as the parts you swap in are used throughout the injustry and meet an objective standard of acceptability, you will be less likely to be found at fault.
Nonetheless, as I tell all of my clients, "anyone can be sued for anything. Whether the plaintiff's case proceeds to trial is within the jurisdiction and caprice of the court." It is best to consult your local insurance defense attorney and District Attorneys office before modifying your firearm to any significant extent.